Fuse protectors for electric circuits having improved terminal means forming a sealed enclosure



Jan. 31, 1967 A. J. FlsTr-:R 3,301,979

FUSE PROTECTORS FOR ELECTRIC CIRCUITS HAVING IMPROVED TERMINAL MEANS FORMING A SEALED ENCLOSURE Filed oct. 22, 1965 United States Patent titice 3 301,979 FUSE PROTECTORS FOR ELECTRIC CIRCUITS HAVING IMPROVED TERMINAL MEANS FORM- ING A SEALED ENCLOSURE Aloysius J. Fister, Overland, M0., assignor t McGraw- Edison Company, Elgin, Ill., a corporation of Delaware Filed Oct. 22, 1965, Ser. No. 501,120

8 Claims. (Cl. Zilli-120) This invention relates to improvements in electric fuses. It is, therefore, an object of the present invention to provide an improved electric fuse.

It is important to embed the fusible elements of some electric fuses within arc-extinguishing ller material. Further, it is important to provide liquid-tight enclosures for some electric fuses. In recognition of these facts electric fuses, such as the electric fuse of Patent No. 2,837,614, have had the fusible elements thereof embedded within arc-extinguishing filler material and have had O-rings to seal the ends of the enclosures thereof. In assembling those fuses, the O-rlngs were set within annular recesses in the peripheries of the end bells of those fuses, and then the fusible elements and end bells of those fuses were telescoped within the enclosures for those fuses. Thereafter, the arc-extinguishing iller rnaterial was introduced into the fuse enclosures through openings in the end bells; and those openings were t-hen closed by plugs to make those enclosures liquid-tight. The use of end bells with openings for the introduction of arc-extinguishing ller material and with annular recesses for O-rings is very practical where the diameters of the end bells are large enough to permit large openings to be formed therein and where the size and number of fusible elements make the current-carrying components of the fuses sturdy and rugged. However, where a fuse has a relatively weak fusible element or fusible elements, the telescoping of the end bells and the fusible element or fusible elements into the enclosure for that fuse, after O-rings have been set Within recesses in those end bells, can subject that fusible element or those fusible elements to severe mechanical stresses. Also, where the end bells of a fuse are small in diameter, it is difficult to introduce arc-extinguishing filler material into the enclosure for that fuse through openings in those end bells.

The present invention makes it possible to use O-rings to seal the ends of the enclosure for a fuse without subjecting the current-carrying components of that fuse to severe mechanical stresses; and it does so by making the end bells of that fuse in separable sections 'which can be assembled together to force the O-rings into sealing engagement with the enclosure for the fuse. Until t-he separable sections of an end bell are assembled together to force an O-ring into sealing engagement with the enclosure for the fuse, those sections and that O-ring can be telescoped within and moved relative to the enclosure for a fuse Without subjecting the current-carrying components of that fuse to severe mechanical stresses. Then, after the fusible element or fusible elements, the separable sections of t-he end bells, and the O-rings have been telescoped within the enclosure for the fuse, those separable sections can be assembled together to force those O-rings into sealing engagement with that enclosure. It is, therefore, an object of the present invention to provide an electric fuse with separable sections which can be assembled together to force O-rings into sealing engagement with the enclosure for the fuse.

The diameters of the inner of the separable sections of the end bells provided by the present invention are appreciably smaller than the inner diameters of the ends of the enclosure for the fuse; and this is desirable because it enables arc-extinguishing filler material to ow 3,301,979 Patented Jan. 31, 1967 freely between the peripheries of those inner sections and the inner surfaces of the ends of that enclosure. Because the arc-extinguishing liller material can ow freely between t-he peripheries of those inner sections and the inner surfaces of the ends of that enclosure, openings do not have to be formed in those separable sections to permit the arc-extinguishing filler material to be introduced into the enclosure for the fuse. To introduce the arc-extinguishing filler material into the enclosure for the fuse, the inner sections of the end bells and the fusible element or fusible elements of that fuse will `be telescoped into position Within that enclosure; and then an O-ring and the outer section of one of the end bells will be assembled with one of those inner sections to close and seal one end of that enclosure. rested on that one end, and arc-extinguishing filler material will be caused to flow between the periphery of the inner section of the other end -bell of that fuse and the enclosure for that fuse. After that enclosure has been filled with arc-extinguishing filler material, the O-ring for that other end bell can be telescoped within that enclosure; and then the outer section of that end bell can be assembled with the inner section of that end bell and tightened to cause the O-ring to form a seal with the enclosure. It is, therefore, an object of the present invention to provide an electric fuse which has an enclosure and which has at least one end `bell thereof made up of separable sections that can force an O-ring into sealing engagement with that enclosure.

Other and further objects and advantages of the present invention should become apparent from an examination of the drawing and accompanying description.

In the drawing and accompanying description a preferred embodiment of the present invention is shown and described but it is to be understood that the drawing and accompanying description are -for the purpose of illustration only and do not limit the invention and that the invention will be defined by the appended claims.

In the drawing, FIG. 1 is a side elevational view of one preferred embodiment of electric fuse that is made in accordance with the principles and teachings of the present invention,

FIG. 2 is a sectional view, on a larger scale, through the electric fuse of FIG. 1, and it is taken along the plane indicated by the line 2 2 in FIG. 1,

FIG. 3 is an elevational View, on a still larger scale, of the right-hand end of the electric fuse of FIG. 1,

FIG. 4 is a sectional view, on the scale of FIG. 3, through the electric fuse of FIG. 1, and it is taken along the plane indicated by the line 4 4 in FIG. 2,

FIG. 5 is another sectional view, on the scale of FIG. 3, through the electric fuse of FIG. 1, and it is taken along the plane indicated by the line 5 5 in FIG. 2,

FIG. 6 is yet another sectional view, on the scale of FIG. 3, through the electric fuse of FIG. 1, and it is taken along the plane indicated by the line 6 6 in FIG. 2, and

FIG4 7 is an exploded view ofthe left-hand end of the electric fuse of FIG. 1.

Referring to the drawing in detail, the numeral 20 generally denotes an electric fuse which has an elongated enclosure 22 of cylindrical configuration. That enclosure is made from insulating material; and glass melamine is one insulating material that is very useful in making that enclosure.

Two end bells or terminals are provided for the fuse 20; and one of those end bells is disposed within the left-hand end of the enclosure 22, while the other of those end bells is disposed within the right-hand end of that enclosure. Those end bells are identical; and hence only one of those end bells, namely, the left-hand end bell, will be described in detail.

That enclosure will then be The numeral 24 denotes the inner section of the lefthand en d bell of the fuse 20; and that inner section has a cylindrical recess 26 in the inner lface thereof, as shown by FIG. 6. That inner section has a shallow annular groove 2S at the exterior thereof, as shown by FIG. 6; and that annular groove is separated from the cylindrical recess 26 by an annular Wall 29. A frusto-conical surface 3) is formed on the inner section 24; and that frustoconical surface is directed away from the annular groove 28. The inner section 24 has a threaded shank 32; and that threaded shank extends to the left in FIGS. 2, 6 and 7. A cylindrical socket 34 is formed within the threaded shank 32, that socket extends inwardly from the left-hand end of that shank, and that socket accommodates a cylindrical rod 36. The inner end of that cylindrical rod will be pressed into position within the cylindrical socket 34; and then it will be bonded to the shank 32 of the inner section 24 by solder 37. In this way, the cylindrical rod 36 will be mechanically-secured and electrically-bonded to the inner `section 24 of the left-hand end bell of the electric fuse 20.

The 'end bell at the right-hand end of the electrical fuse 20 will have an inner section which is identical to the inner section 24; and a cylindrical rod 38 will be mechanically-secured and electrically-bonded within the cylindrical socket in the threaded shank of that other end bell. The cylindrical rods 36 and 38 will be used to connect the electric fuse 20 into the circuit which that fuse will protect.

The numeral 40 denotes an elongated bridge of insulating material; and the ends of that bridge of insulating material extend into the cylindrical recesses 26 in the inner faces of the inner sections 24 of the end bells at the opposite ends of the electric fuse 20. That bridge of insulating material could be made in different configurations, but it is shown as being -cruciform in configuration and as having radially-extending projections 41 intermediate the ends thereof. Those projections are intended to be disposed immediately adjacent the inner surface of the enclosure 22 and to keep the rest of the bridge 40 of insulating material from engaging that interior. `An elongated wire-like fusible conductor 42 is wound in generally helical fashion around the bridge 40;

and a mass 44 of solder secures one end of that fusible conductor to the annular wall 29 of the inner section 24 of the end bell at the left-hand end of the fuse 20, while another mass 44 of solder secures the other end of that fusible conductor to the annular wall 29 of the inner section 24 of the end bell at the right-hand end of that fuse. The fusible conductor 42 electrically inter-connects the inner sections 24 of the end bells at the opposite ends of the fuse 26, and that fusible conductor will carry the rated current of the fuse plus harmless overloads. However, that fusible conductor will respond to potentially hurtful overloads to fuse and thereby interrupt the circuit.

The numeral 46 denotes the outer section of the end bell at the left-hand end of the fuse 20, land that outer section has a frusto-conical surface 48 which will -confront the frusto-conical surface 30 on the inner section 24 of that end bell. A slot 50 is formed in the outer face of the outer section 46, and that slot extends diametrically of that outer member. A threaded passage 52 extends axially through the outer section 46, and that threaded passage communicates with the slot 50. An identical outer section 46 is provided for the end bell at the right-hand end of the fuse 20.

It will be noted that the diameters of the outer sections 46 are just slightly smaller than the inner diameter of the enclosure 22, whereas the diameters of the inner sections 24 are appreciably smaller than the inner diameter of that enclosure. The smaller diameters of the inner sections 24 are important; because they enable arc-extinguishing filler material 62, such as sand, vcalcium sulfate, or the like, to be introduced into the enclosure 22 even though the diameters of the end bells are so small that passages for arc-extinguishing ller material cannot be provided in those end bells.

In assembling the electric fuse 20 of FIG. l, the opposite ends of the bridge 40 are telescoped into the cylindrical recesses 26 in the inner faces of the inner sections 24 ofthe end bells for that fuse. A bonding material 55, such as an epoxy resin, .is then introduced into each of the cylindrical recesses 26 to xedly bond the ends of the bridge 40 to the inner sections 24. Thereafter,'the yfusible conductor 42 is wound in generally helical fashion upon the bridge 40, and the masses 44 of solder are used to mechanically secure and electrically bond the ends of that fusible conductor to the annular walls 29 of the inner sections 24 of the end bells. At this time, the inner sections 24, the cylindrical rods 36 and 38, the bridge 40, and the fusible conductor 42 constitute a rugged and sturdy sub-assembly which can be readily handled as a unit. That sub-assembly can easily be telescoped within the enclosure 22, because the diameters of the inner sections 24 are appreciably smaller than the inner diameter of that enclosure. Once that sub-assembly has been telescoped within the enclosure 22, an O-ring 56 of resilient material can be telescoped within the right-hand end of that enclosure and moved into abutting engagement with the frusto-conical face 30 on the inner section 24 of the end bell at that end of that enclosure. That O-ring can easily be telescoped within that right-hand end of that enclosure because that O-ring will be substantially unstressed, and the normal outer diameter of that O-ring will not be appreciably greater than the inner diameter of that enclosure. Thereafter, the threaded passage 52 in the outer section 46 of the end bell at the right-hand end of the enclosure 22 will be telescoped over the cylindrical rod 38 and moved into engagement with the threaded shank on the inner section of that end bell. The assembler will hold that 'shank stationary by gripping the cylindrical rod 36 at the other end of the fuse 20, and will then rotate the outer section 46 at the right-hand end of the enclosure 22 in the clockwise direction in FIG. 3 by inserting the blade of a screw driver or other tool in the slot 50. That rotation of that outer section will move the frusto-conical surface 48 on that outer section into engagement with the O-ring S6; and continued rotation of that outer section `will enable that frusto-conical surface to coact with the frusto-conical surface 30 on the inner section 24 to compress that O-ring. That O-ring will respond to that compression to deform into intimate and sealing engagement with the inner surface of the enclosure 22, with the frusto-conical surface 48 on the outer section 46, and with the frusto-conical `surface 30 on the inner section 24. As a result, a liquid-tight seal will be provided between the enclosure 22 and the end bell at the right-hand end of the fuse 20.

Thereupon, the fuse 20 can be set so it is vertically disposed and so it is resting upon the outer end of the cylindrical rod 38; and then arc-extinguishing ller material 62 can be introduced into the upper end, the left-hand end shown in FIG. 1, of the enclosure 22. That arc-extinguishing ller material will readily llow downwardly through the annular space between the periphery of the inner section of the left-hand end bell of the fuse 20 and the inner surface of theenclosure 22 to till that enclosure.. That arc-extinguishing filler material ywill engage and embed the fusible conductor 42 and will also engage and embed the bridge 40.

After the enclosure 22 has been filled with arc-extinguishing filler material 62, a second O-ring 56 will be telescoped inwardly of the upper end-t-he left-hand end shown in FIG. l-of that enclosure; and that O-ring will be moved into abutting engagement with the frustoconical surface 30 on the inner section 24 of the end ybell at that end of that enclosure. That O-ring can easily be telescoped within that end of that venclosure because that O-ring will be substantially unstressed, and the normal outer diameter of that O-ring will not lbe appreciably greater than the inner diameter of that enclosure. Thereafter the threaded passage 52 in the outer section 46 of the end bell at the upper end of the enclosure 22 will be telescoped over the cylindrical rod 36 and moved into engagement with the threaded shank 32 of the inner section 24 of that end bell. The assembler will then rotate that outer section until the frusto-conical surface 48 thereon coacts with the frusto-conical surface 30 on the inner section 24 of the upper end bell to compress the O-ring 55 there between. That O-ring will respond to that compression to deform and move into intimate and sealing engagement with the inner surface of the enclosure 22,

. with the frusto-conical surface 48 on the outer section 46,

and with the frusto-conical surface 30 on the inner section 24. As a result, a liquid-tight seal will be provided between the enclosure 22 and the end bell at the upper end of the enclosure 22.

In this way, the present invention makes it easy and simple to dispose the end bells and the fusible element or fusible elements of the fuse within the enclosure for that fuse, to provide a liquid-tight seal between one of the end `bells of that .fuse and that enclosure, to permit easy filling of that enclosure with arc-extinguishing filler material, and then to provide a liquid-tight seal between the other end bell of that fuse and the enclosure of that fuse. Significantly, the present invention avoids all need of applying heavy, axially-directed pressures to the bridge 40 during the assembling of the fuse.

The provision of an annular space, between the periphery of an inner section 24 of an end Ibell and the inner surface of the enclosure 22, to permit arc-extinguishing filler material 62 to enter the enclosure 22, is desirable, because it enables that arc-extinguishing filler material to engage and embed all surfaces of the bridge 40 and the fusible conductor 42. Further, it minimizes the possibility of the arc-extinguishing filler material 62 failing to fill all portions of the enclosure 22. As a result, the present inventi-on substantially keeps empty spaces from developing within the enclosure 22; and hence any arc which tends to form as the fusible conductor 42 fuses will quickly be extinguished by the arc-extinguishing filler material 62.

If an empty space should, somehow, develop in the enclosure 22, and if that enclosure were to be set in vertical position when the fuse 20 was in use; that empty space would be adjacent the inner section 24 of the upper end bell. That inner section will be spaced inwardly from the inner surface of the enclosure 22 to define an annular area; and the annular groove 2S will be spaced even further inwardly from that inner surface of that enclosure to define an even larger annular area. Both of those annular areas are displaced axially from the fusible portions of said fusible conductor 42; and hence any empty spaces in either of those annular areas would not keep the arc-extinguishing filler material 62 from completely embedding all fusible portions of the fusible conductor 42.

After the outer sections 46 have been solidly secured to the inner sections 24 of the end bells, a drill will be used to form openings in the ends vof the enclosure 22 and to form sockets 54 in those outer sections. Thereafter, pins 58 and 60 will be pressed into position within those openings, and within those sockets, to prevent rotation of the outer sections 46 of the end bells relative to the enclosure 22.

In some instances, the fusible conductor 42 will be replaced by a ribbon-like fusible conductor which has one or more weak spots therein. However, the replacement of that fusible conductor will not change the manner of assembling the fuse 2f] or the manner of filling the enclosure 22 of that fuse.

Whereas the drawing and accompanying description have shown and described a preferred embodiment of the present invention it should be apparent to those skilled in the art that various changes may be made in the form ot the invention without affecting the scope thereof.

What I claim is:

1. An electric fuse that comprises:

(a) an enclosure,

(b) an end bell that is disposed within one end of said enclosure and that has separable sections,

(c) one of said separable sections of said end bell having a sealing surface thereon,

(d) a second separable section of said end bell having a sealing surface thereon that can confront said sealing surface on said one separable section of said end bell,

(e) said one and said second separable sections of said end bell being securable in assembled relation,

(f) a sealing element that is disposed within said one end of said enclosure and that is compressed by said sealing surfaces on said one and said second separable sections of said end bell to form a seal between the interior surface of said one end of said enclosure and said separable sections of said end bell,

(g) a second end bell that is disposed within the other end of said enclosure,

(h) a fusible conductor having one end thereof secured to said one separable section of the first said end bell and having the other end thereof secured to said second end bell,

(i) said second separable section of the first said end bell being dimensioned to move relative to said enclosure while it is disposed within said one end of said enclosure, and

(j) a bridge that is secured to said one separable section of the first said end bell and to said second end bell to support said fusible conductor,

(k) said separable sections of the first said end bell permitting said fusible conductor, said bridge, said one separable section of the first said end bell, said sealing element, and said second section of the first said end bell to be disposed within said enclosure without any need of subjecting said fusible conductor to severe mechanical stresses.

2. An electric fuse that comprises:

(a) an enclosure,

(b) an end bell that is disposed within one end of said enclosure and that has separable sections,

(c) said one separable section of said end bell having a sealing surface thereon,

(d) said one separable section of said end bell having a diameter smaller than the inner diameter of said one end of said enclosure, whereby said one separable section of said end bell and said one end of said enclosure can coact to define an annular space through which arc-extinguishing filler material can be introduced into said enclosure,

(e) a second separable section of said end bell having a sealing surface thereon,

(f) a sealing element that is disposed within said one end of said enclosure and that is compressed by said sealing surfaces of said one and said second separable sections of said end bell to form a seal between the interior surface of said one end of said enclosure and said separable sections of said end bell,

(g) a second end bell that is disposed within the other end of said enclosure,

(h) a bridge of insulating material with one end thereof extending to said one separable section of the first said end bell and with the other end thereof extending to said second end bell, Y

(i) securing material fixedly securing said bridge to said one separable section of the first said end bell and to said second end bell,

(j) a fusible conductor mounted on said bridge and having one end thereof secured to said one separable section of the first said end bell and having the other end thereof secured to said second end bell, and

(k) arc-extinguishing ller material disposed within said nclosure and embedding said bridge and said fusible conductor.

3. An electric fuse that comprises:

(a) an enclosure,

(b) an end bell that is disposed within one end of said enclosure and that has separable sections,

(c) said one separable section of said end bell having a sealing surface thereon,

(d) said one separable section of said end bell having a diameter smaller than the inner diameter of said one end of said enclosure, whereby said one separable section of said end bell and said one end of said enclosure can coact to define an annular space through which arc-extinguishing filler material can be introduced into said enclosure,

(e) a second separable section of said end bell having a sealing surface thereon,

(f) a sealing element that is disposed within said one end of said enclosure and that is compressed by said sealing surfaces of said one and said second separable sections of said end bell to form a seal between the interior sur-face of said one end of said enclosure and said separable sections of said end bell,

(g) a second end bell that is disposed within the other end of said enclosure,

(h) a bridge of insulating material with one end thereof etxending to said one separable section of the rst said end bell and with the other end thereof eX- tending to said second end bell,

(i) securing material lixedly securing said bridge to said one separable section of the first said end bell and to said second end bell,

(j) a fusible conductor mounted on said bridge and having one end thereof secured to said one separable section of the rst said end bell and having the other end thereof secured to said second end bell, and

(k) arc-extinguishing filler material disposed within said enclosure and embedding said bridge and said fusible conductor,

(l) said sealing surfaces being frusto-conical in configuration,

(m) said sealing element being an O-ring,

(n) said O-ring having an unstressed outer diameter close to the inner diameter of said one end of said enclosure,

(o) whereby said O-ring is easily telescoped into said one end of said enclosure.

4. An electric fuse that comprises:

(a) an enclosure,

(b) an end bell that is disposed within one end of said enclosure and that has separable sections,

(c) one of said separable sections of said end bell having a sealing surface thereon,

(d) said one separable section of said end bell having a diameter smaller than the inner diameter of said one end of said enclosure,

(e) a second separable section of said end bell having a holding surface thereon that is complementary to a holding surface on said one separable section of end bell,

(f) said second separable section of said end bell having a sealing surface thereon that can confront said sealing surface on said one separable section of said end bell,

(g) said second separable section of said end bell having a diameter smaller than the inner diameter of said one end of said enclosure,

(h) a sealing element that is disposed within said one end of said enclosure and that is compressed by said scaling surfaces of said one and said second separable sections of said end bell to -form a seal between the interior surface of said one end of said enclosure and `said separable sections f Said end bell,

(i) a second end bell that is disposed within the other end of said enclosure,

(j) a fusible conductor having one end thereof secured to said one separable section of the first said end bell and having the other end thereof secured to said second end bell,

(k) said separable sections of the first said end bell permitting said fusible conductor, said one separable section of the rst said end bell, said sealing element, and said second section of the first said end bell to be disposed within said enclosure without any need of subjecting said fusible conductor to severe mechanical stresses.

5. An electric fuse that comprises:

(a) an enclosure,

(b) an end bell that is disposed within one end of said enclosure and that has separable sections,

(c) one of said separable sections of said end bell having a sealing surface thereon,

(d) said one separable section of said end bell having a diameter smaller than the inner diameter of said one end of said enclosure,

(e) a secondseparable section of said end bell having a holding surface thereon that is complementary to a holding surface on said one separable section of said end bell,

(f) said second separable section of said end bell having a sealing surface thereon that can confront said sealing surface on said one separable section of said end bell,

(g) said second separable section of said end bell having a diameter smaller than the inner diameter of said one end of said enclosure,

(h) a sealing element that is disposed within said one end of said enclosure and that is compressed by said sealing surfaces of said one and said second separable sections of said end bell to form a seal between the interior surface of said one end of said enclosure and said separable sections of said end bell,

(i) a second end bell that is disposed within the other end of said enclosure,

(j) a fusible conductor having one end thereof secured to said one separable section of the first said end bell and having the other end thereof secured to said second end bell,

(k) said separable sections of the first said end bell permitting. said fusible conductor, said one separable section of the first said end bell, said sealing element, and said second section of the rst said end bell to be disposed ,within said enclosure without any need of subjecting said fusible conductor to severe mechanical stresses.

(l) said sealing elements being O-rings that have unstressed outer diameters close to the inner diameters of said ends of said enclosure,

(m) said sealing surfaces being frusto-conical in configuration.

6. An electric fuse that comprises:

(a) an enclosure,

(b) an end bell that is disposed within one end of said enclosure and that has separable sections, (c) one of said separable sections of said end lbell having a sealing surface thereon,

(d) said one separable section of said end bell having a diameter smaller than the inner diameter of Said one end of said enclosure,

(e) a second separable section of said end bell having a holding surface thereon that is complementary to a holding surface on said one separable section of said end bell,

(f) said second separable section of said end bell having a sealing surface thereon that can confront said sealing surface on said one separable section of said end bell,

(g) said second separable section of said end bell having a diameter smaller than the inner diameter of said one end of said enclosure,

(h) a sealing element that is disposed within said one end of said enclosure and that is compressed by said sealing surfaces of said one and said second separable sections of said end bell to form a seal between the interior surface of said one end of said enclosure and said separable sections of said end bell,

(i) a second end bell that is disposed within the other end of said enclosure,

(j) a fusible conductor having one end thereof secured to said one separable section of the first said end bell and having the other end thereof secured to said second end bell,

(vk) said separable sections of the first said end bell permitting said fusible conductor, said one separable section of the rst said end bell, said sealing element, and said .second section o-f the first said end bell to be disposed `within said enclosure Without any need of subjecting said fusible conductor to severe mechanical stresses,

(l) said one separable section of the lfirst said end bell being spaced from the inner Isurface of said one end of said enclosure to define an annular area through which arc-extinguishing filler material can be intro- -d-uced into said enclosure, and

(m) arc-extinguishing filler material disposed Within said enclosure and embedding said fusible conductor.

7. An electric fuse that comprises:

(a) an enclosure,

('b) an end bell that is disposed within one end of said enclosure and that has separable sections,

(c) one of said separable sections of said end bell having a sealing surface thereon,

(d) said one separable section of said end ibell having a diameter smaller than the inner diameter of Said one end of said enclosure,

(e) a second separable section of said end bell having a holding surface thereon that is complementary to a holding surface on said one separable section of said end bell,

(f) said second separable section of said end bell having a sealing surface thereon that can confront said sealing surface on said separable section of said end bell,

('g) said second separable section of said end bell havying a diameter smaller than the inner diameter of said one end of said enclosure,

(h) a sealing element that is disposed within said one end of said enclosure and that is compressed by said sealing surfaces of said one and said second separable sections of said end bell to form a seal between the interior surface of said one end of said enclosure and said separable sections of said end bell,

(i) a second end bell that is disposed within the other end of said enclosure,

(j) a sturdy bridge that has one end thereof lixedly secured to said one separable section of the first said end `bell and that has the other end thereof fixedly secured to said second end bell, and

(k) a fusi-ble conductor supported by said bridge and having one end thereof secured to said one separable section of the first said end bell and having the other end thereof secured to said second end bell,

(l) said separable sections of the rst said end bell permitting said vfusible conductor, said bridge, said one separable section of the -rst said end bell, said sealing element, and said second section of the first said end bell to be disposed within said enclosure without any need for subjecting said fusible conductor to severe mechanical stresses,

(m) said bridge enabling said holding surfaces on said separable sections of the first said end Ibell to be moved into holding engagement with each other without subjecting said tfusible conductor to severe mechanical stresses.

8. An electric fuse that comprises:

(a) an enclosure,

(b) an end bell that is disposed within one end of said enclosure and that has separable sections,

(c) one of said separable sections of said end bell having a sealing surface thereon.

(d) said one separable section of said end bell having `a diameter smaller .than the inner diameter of said one end of said enclosure, whereby said one separable section of said end bell and said one end of said enclosure can coact to define an annular space through which arc-extinguishing ller material can be introduced into said enclosure,

(e) a second separable section of said end bell having a holding surface thereon that is complementary to a holding surface on said one separable section of said end bell,

(f) said second separable section of said end bell having a sealing surface thereon,

(g) a sealing element that is disposed within said one end of said enclosure and that is compressed by said sealing surfaces of said one and said second separable sections of said end bell to form a seal between the interior surface of said one end of said enclosure and said separable sections of said end bell,

(h) said sealing element acting, whenever it is compressed, to block said annular space between said one separable section of said end bell and said one end of said enclosure,

(i) a second end bell that is disposed within the other end of said enclosure,

(j) a fusible conductor connected to said and (k) arc-extinguishing ller material disposed within said enclosure and embedding said fusible conductor.

end bells,

References Cited by the Examiner UNITED STATES PATENTS 2,071,435 2/ 1937 Saudicoeur 20G-131 X 2,308,435 1/1943 Wood 200-131 2,761,932 9/1956 Kozacka et al. 200-132 X 2,837,614 6/1958 Fister 20G-120 BERNARD A. GILHEANY, Primary Examiner.

B. GILSON, Assistant Examiner. 

1. AN ELECTRIC FUSE THAT COMPRISES: (A) AN ENCLOSURE, (B) AN END BELL THAT IS DISPOSED WITHIN ONE END OF SAID ENCLOSURE AND THAT HAS SEPARABLE SECTIONS, (C) ONE OF SAID SEPARABLE SECTIONS OF SAID END BELL HAVING A SEALING SURFACE THEREON, (D) A SECOND SEPARABLE SECTION OF SAID END BELL HAVING A SEALING SURFACE THEREON THAT CAN CONFRONT SAID SEALING SURFACE ON SAID ONE SEPARABLE SECTION OF SAID END BELL, (E) SAID ONE AND SAID SECOND SEPARABLE SECTIONS OF SAID END BELL BEING SECURABLE IN ASSEMBLED RELATION, (F) A SEALING ELEMENT THAT IS DISPOSED WITHIN SAID ONE END OF SAID ENCLOSURE AND THAT IS COMPRESSED BY SAID SEALING SURFACES ON SAID ONE AND SAID SECOND SEPARABLE SECTIONS OF SAID END BELL TO FORM A SEAL BETWEEN THE INTERIOR SURFACE OF SAID ONE END OF SAID ENCLOSURE AND SAID SEPARABLE SECTIONS OF SAID END BELL, (G) A SECOND END BELL THAT IS DISPOSED WITHIN THE OTHER END OF SAID ENCLOSURE, (H) A FUSIBLE CONDUCTOR HAVING ONE END THEREOF SECURED TO SAID ONE SEPARABLE SECTION OF THE FIRST SAID END BELL AND HAVING THE OTHER END THEREOF SECURED TO SAID SECOND END BELL, (I) SAID SECOND SEPARABLE SECTION OF THE FIRST SAID END BELL BEING DIMENSIONED TO MOVE RELATIVE TO SAID ENCLOSURE WHILE IT IS DISPOSED WITHIN SAID ONE END OF SAID ENCLOSURE, AND (J) A BRIDGE THAT IS SECURED TO SAID ONE SEPARABLE SECTION OF THE FIRST SAID END BELL AND TO SAID SECOND END BELL TO SUPPORT SAID FUSIBLE CONDUCTOR, (K) SAID SEPARABLE SECTIONS OF THE FIRST SAID END BELL PERMITTING SAID FUSIBLE CONDUCTOR, SAID BRIDGE, SAID ONE SEPARABLE SECTION OF THE FIRST SAID END BELL, SAID SEALING ELEMENT, AND SAID SECOND SECTION OF THE FIRST SAID END BELL TO BE DISPOSED WITHIN SAID ENCLOSURE WITHOUT ANY NEED OF SUBJECTING SAID FUSIBLE CONDUCTOR TO SEVERE MECHANICAL STRESSES. 